This book constitutes the proceedings of the 16th International Workshop on Security and Trust Management, STM 2020, co-located with the 25th European Symposium on Research in Computer Security, ESORICS 2020. The conference was planned to take place in Guildford, UK, but had to be moved to an online format due to the COVID-19 pandemic. The workshop took place during September 17-18, 2020. The 8 papers presented in this volume were carefully reviewed and selected from 20 submissions. They were organized in topical sections on security properties and attacks; confidentiality schema and security processes.